Process of improving armor-plates.



,NITED STATES :MIL nnnnNsnnRcnR, or assure, GERMANT, ASSIGNOR T FRIED. KRUPP, or SAME PLACE.

Pnocsss oF-iM Rovme ARMoR-PLA'TEs.

srncmxca'rxon forming part of Letters me No. 653,413, dated July 10, 1900.

Original application filed April 21, 1896, Serial lio- 689,.513.' Divided and this application filed October 19, 1899. Serial No.

.734,l13- (Ho specimens.) I

To all whom it 11mg concern:

Be it known that I, EMIL EHRENSBERGER, a citizen of the German Empire, residing at Essen, Germany, have invented certain new and useful Improvements in Processes of Improving Armor-Plates, of which the follow ing is a specification, and which invention formed part of an application filed by me April 21, 1896, Serial No. 588,513.

The method or process forming the subject of the present invention has for its object the improvement of steel armor-plates by imparting to the side theregi which is exposed to the impact or? projectiies the greatestsuia 1 able hardness and to the other 'side thereof the greatest toughness which the armor-plate material can acquire. By such construction and the mode of. manufacture hereinafter described is obtained the greatest resistance to cracking and the highest degree of strength. \Vith this object in view my invention consists, edsentially, in heating the side of the plate to be hardened to a temperature corresponding to the degree of hardness desired,. 2 5 while heating the other side, which is to become tough, to a heat below that necessary to produce hardening, but high enough to produce toughening, and then cooling suddenly only the side which has been heated to' 0 the higher temperature. After steel armorplates have been improved in quality by being suddenly cooled down from a high temperature that renders the molecules capable of an easy rearrangement they may be made 5 to acquire the quality of extreme toughness by being heated a second time toalower temperature than the first heating and by being allowed to cool slowly down from said rem:

perature. These respective high tempera- 0 tures will vary with the nature and compo sition of the steel, and hence directions cannot be given in exact degrees of temperature; but the first heating should be of such high degree as will permit easy flow or rearrange- 5 ment of the molecules, and this may be obtained by heating up to about, say, 800 to 1,000 centigrade, but should stop short of the meltingpoint; but in order that the r armor-plate shall combine the most eflicient est degree of toughness oflthe other side I treat the plate in the following manner: The plate is first improved in quality by being heated, as above described, to the high temperature which permits an easy or ready flow or rearrangement of the molecules, and-the entire plate-is then suddenly cooled from such temperature by immersion or spraying in the usual manner. I call this the quality-improving heat. By this means the steel ac 6o quires not only considerablehardness, but also an extreme fineness of grain 'or texture, which makes it capable of subsequently ac 'quirin'gthe greatest degree of toughness; but as the hardness'is now too great to allow of machining or' shaping the plate the temper should be then drawn and the plate be then machined or shaped as may be desired, or the plate is heated to a temperature at which hardening will not take place and the plate is then cooled suddenly from this tern. peraturc. Then the plate can be'machined or shaped while cold. This heat I call the annealing heat. The plate having been thus properly worked, one sidevi z., the side intended to be exposed: to the impactotprojectiles-is heated to a temperature adapted to produce the required degree of hardness. This I call the hardening heat, and the other or rear side is heated to a temperature below that to which the exposed side is heated. This latter temperaturecshould-be such as to produce toughness in the highest degree and will be a red heat. This I call the toughening heat. The hardening heat 8 ranges from 750 to 900,centigrade, according to the intensity of the quality-improving neaunnu' the-toughening heat rangesfrnnr 500 to 700 centigrada; The plate is then suddenly cooled by immersing or spraying only that side which is intended to acquire maximum hardness; but if this treatment is not sufficient, as in the case of aQvery thick plate, to causethe rear side oi the plate to acquire suiiicienttoughness then the ent re plate should be immersed or sprayed. The operation of immersing or spraying one side -of the plate may be adopted when owing to the material employed the rear side elf-the 50 degree of hardness of one side and the greatplate would become hard by the immersion mo' re 01" the process. For instance, the e hardened on (me side only may aeriel to them a, suitable grain or being rolled at alow temperature :ir parts are differently heated. [claim as new is I 1. e herein-described process for impartinl hardness '00 on e side an ('1 maximum .mess to the other side of plates made of ,0? mixture of steel capable of being mnsieting in heating the side hardened to a temperate re corf to the degree of hardness desired, .in the Other side, which is to be- "ii, to a heat below that necessary e hardening but high enough to proiening, and then cooling suddenly side which has been heated to the (immature.

V to the other side of plates made of mixmren of steel capable (if being; consisting in first subjecting the l'iign temperature permitting an hardened to a temperature correw the degree of hardness desired, 5* the other side, which is to i, L0 it lower new mid beluw suddeniy only the side which ed t0 'Zheliigher temperature.

' zerein-deeeribed process forimpm'bimrdness toonesizleand maximum LilG other side of platesmnde of 'mizanmes of steel capable of being ,onsisting in first subjecting the high temperature permitting an Mr reerrzmgemenil,then smlzlenly a, then healing the plate to :1/ gli enonglg' to produce liar- '=n cooling and simping the plate tixen reheating; the side of the I 4 L0 be hardened to n ten'iperw re eerrespmnling to the de ree of hardness fie heating the ntliersidewhich is! gh to :1, red heat llOlOWl l'iiLlil'lMF mince hardening, and then 0001- .35" only the side which lm l been I igller lern mz'nim'e. imnuy whereof i have hereunto 304'; (l in me 'n'erience of two subscribing will 1 1 eulm' rearrangement,then suddenly 0e, then heating the side which .r to produce hardening, and 

